Chemistry of inorganic compounds – Oxygen or compound thereof – Metal containing
Patent
1986-07-16
1988-08-30
Edlow, Martin H.
Chemistry of inorganic compounds
Oxygen or compound thereof
Metal containing
357 78, 423334, 423338, 2521814, H01L 2328
Patent
active
047680814
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to encapsulated microelectronic circuits or circuit elements with organic components, whereby a getter is incorporated within the inner chamber for absorbing corrosive gases.
DESCRIPTION OF THE PRIOR ART
Due to the practical requirements imposed on such circuits or circuit elements, highly reliable electronic circuits are protected against environmental influences, moisture, CO.sub.2, SO.sub.2, as well as other corrosive agents by means of hermetic welding or soldering to a metal or ceramic housing. On the other hand, more and more organic materials are being used for passivating, die-bonding, and for a covering against mechanical shocks in the construction of electronic circuits. However, under thermal loading as occurs in hybrid power systems and partially, that is to a smaller extent, in small-signal circuits, a small gas generation must be expected even in thermally stable epoxy-, polyurethane-, and silicone-resins or elastomers of proven reliability in microelectronics. It is known through gas analysis, that the gases involved are mostly H.sub.2 O, CO.sub.2, CO, NH.sub.3, and organic acids, which lead to an electrolytic corrosion of aluminum conduction paths and of bond wires, thereby causing failure of the circuit, in hybrid systems to which a voltage is applied. The hereby resulting hydrogen as well as any remaining oxygen increase the corrosion, so that these gases should be removed.
In low power hybrids, these gases partially precipitate as moisture and cause additional electrolysis when a voltage is applied. The formation of aging-, or fission-products may only be prevented to a limited extent in spite of exhaustive efforts in applying processing technology, for example evacuation N.sub.2 -flushing, or drying. The drying agents used in electronics and known for example from the German Patent Publication (DE-OS) No. 3,112,564 or the molecular sieves based on zeolith, the use of which is known, for example from European Patent Publication (EP-Al) No. 0,113,282, only absorb the moisture and again release the moisture when the circuit is heated, that is under critical switching or operating conditions.
Furthermore, it is suggested, for example in European Patent Publication (EP-A2) No. 0,025,647, to only use partially cross-linked silicone rubber as a getter or as a collector for dust particles. A dust collector obviously does not work as a gas getter and does not absorb moisture.
More suitable are highly active getter materials, which are distributed by vaporization to provide large surface areas, and which irreversibly intercept any reactive gases, perhaps maintain the vacuum stabile and prevent any gas reaction.
Such highly active getters were developed for electron beam tubes for absorbing corrosive gases and moisture traces. Preferably used for this purpose are alkaline earth-, and zirconium metal-, and zirconium hydride-rods, which are vaporized and which, when heated, react more or less strongly with the resulting fission gases, corresponding to barium, in the following reactions.
______________________________________ 2 Ba + H.sub.2 O = Ba H.sub.2 + Ba O
5 Ba + 2 CO.sub.2 =
Ba C.sub.2 + 4 Ba O
3 Ba + CO = Ba C.sub.2 + 2 Ba O
2 Ba + 2 NH.sub.3 =
Ba H.sub.2 + Ba (NH.sub.2).sub.2
2 Ba + 2 R--COOH = Ba (R--COO).sub.2 + Ba H.sub.2
Ba + H.sub.2 = Ba H.sub.2
______________________________________
Extremely fine grained BaAl.sub.4 getters appear, at first, to be especially suited for use as the organic materials or the resulting fission gases used in electronic circuits, because such getters are inert relative to "kovar" or chrome-nickel steel and are relatively stable with respect to nitrogen, but absorb or chemically absorb all remaining gases. However, a vaporization of the getter in a small housing is difficult.
OBJECT OF THE INVENTION
It is the aim of the invention to provide processes and materials suitable for carrying out these processes, which make it possible for a getter to reliably render harmless the corrosi
REFERENCES:
patent: 3007089 (1961-10-01), King
patent: 3181229 (1965-05-01), Haberecht et al.
patent: 3885304 (1975-05-01), Kaiser et al.
patent: 4077899 (1978-03-01), van Gils
patent: 4163072 (1979-07-01), Soos
patent: 4342662 (1982-08-01), Kimura et al.
Edlow Martin H.
Fasse W. G.
Kane, Jr. D. H.
Key Gregory A.
Messerschmitt-Boelkow-Blohm GmbH
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